Lightroom doesn’t provide a dedicated Smart Collection rule for “virtual copy.”

The usual workaround is to create a Smart Collection with this rule:

• File Name / Type → Copy Name → isn’t empty

That will often gather your virtual copies, since virtual copies commonly have a Copy Name value.

However, it is not completely foolproof. Copy Name is user-editable metadata, so it can potentially be added, removed, or changed in ways that don’t perfectly identify virtual copies. In other words, Lightroom has no fully reliable Smart Collection criterion for virtual copies alone.

So the short answer is:

• No true built-in virtual-copy filter exists
• Best workaround: use Copy Name isn’t empty